This invention relates to the extraction of metallic, magnetic particles from a liquid coolant utilized in a machining operation.
Ferrous magnetic particles suspended in flowing coolant fluid are of such size as to interfere with the porosity of commonly used grinding wheels and the like causing them to glaze over. When the grinding wheels become glazed over, it then becomes necessary to cutoff the surface which has been glazed before it can be used again. This requires the use of a diamond cutting tool and it causes the grinding wheel to rapidly wear out. In the case of carbide tool tips, used for example on a lathe, the small particles of ferrous metal get caught between the work and the tool causing the tool to become dull by abrasion and wear out quickly causing a necessity for sharpening or reshaping the tool.
Moreover, when the ferrous particles remain in the coolant fluid, rusting or oxidation occurs releasing hydrogen lowering the pH causing the coolant fluid to turn rancid causing bacteria to grow which when coming in contact with human flesh can cause dermatitis or other skin infections. Such makes disposal of the contaminated coolant fluid expensive and hazardous to the sewage systems. By utilization of soda ash it is possible to raise the pH but such chemical additions are expensive and alter the chemical structure of the expensive coolant fluid so that it does not work as effectively and has to be replaced.
Efforts to remove ferrous metal particles from coolant fluid used in machine tools include what is known as the Hydromation process which utilizes suction and paper filters. The particles which cause the problem dealt with by the apparatus and method of this invention are those as may pass through the filters utilized as in the Hydromation process and are so small as to float in the aqueous coolant fluid during use. The larger particles are removed as well as the smaller particles by the apparatus and process of the present invention. The smaller particles may, for example, range in size from about 1-5 Microns.
It is common practice to utilize magnetic devices for removing tramp metal in grain or feed such as illustrated in U.S. Pat. No. 4,457,838. Other applications of magnetic devices to remove magnetic material include magnetic traps disposed in flow lines where non-metallic covers are provided for the traps having depending open ended tubes into which the magnets are inserted for partial shielding from magnetic particles. Such devices are illustrated in U.S. Pat. No. 5,043,063. U.S. Pat. Nos. 2,789,655 and 4,333,825 further illustrate the state of the art.
It would be desirable to remove small or microscopic particles from coolant after the larger pieces of magnetic material are removed by conventional means such as Hydromation or centrifugal separators or all the particles may be removed at one time by utilizing the apparatus and method of the present invention.